BenchReference

#18 Drill Bit

Decimal inches 0.1695″
Millimeters 4.305 mm
System Number (wire gauge)

Nearest equivalents in other systems

System Nearest drill Size Difference
Metric 4.3 mm 0.1693″ / 4.3 mm −0.005 mm (−0.0002″)
Fractional inch 11/64″ 0.1719″ / 4.366 mm +0.06 mm (+0.0024″)
Letter A 0.2340″ / 5.944 mm +1.638 mm (+0.0645″)
−0.344 mm+0.344 mm#18#20−0.216 mm#19−0.089 mm#17+0.089 mm#16+0.19 mm4.3 mm−0.005 mm11/64″+0.06 mmA +1.638 mm →tick position = true diameter · number neighbors above, equivalents below · window ±0.34 mm
Positive difference = cuts a slightly larger hole than #18. Sizes beyond the window are listed with arrows — they are not close substitutes.

Clearance drill for

Thread Fit
#6-32 UNC normal
#6-40 UNF normal

Neighboring number sizes

Drill Decimal in mm vs #18
#20 0.1610 4.089 −0.216 mm
#19 0.1660 4.216 −0.089 mm
#18 0.1695 4.305 —
#17 0.1730 4.394 +0.089 mm
#16 0.1770 4.496 +0.19 mm
Data provenance. ASME B94.11M, Twist Drills (standard drill size series) (ASME). Millimeter and inch values are converted with the exact definition 1 in = 25.4 mm; the canonical dimension for this number size is 0.1695″. See all data sources.